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/*! \file
    \brief Defines a matrix object intended for storing data in registers and
   operations within a CUDA thread.
*/
#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/array.h"
#include "cutlass/matrix_coord.h"

namespace cutlass {
namespace thread {

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Per-thread matrix object storing a packed matrix
template <typename Element, int Rows, int Columns,
          typename Layout = layout::RowMajor>
class Matrix : public Array<Element, Rows * Columns> {
public:
    // Verify layout refers to a rank=2 matrix.
    static_assert(Layout::kRank == 2,
                  "Layout type must refer to a rank=2 matrix");

    /// Base type
    using Base = Array<Element, Rows * Columns>;

    /// Element type
    using Element = Element_;

    /// Number of rows
    static int const kRows = Rows;

    /// Number of columns
    static int const kColumns = Columns;

    /// Layout within the array
    using Layout = Layout_;

    /// Reference type to an element
    using Reference = Element&;

    /// Logical rank of tensor index space
    static int const kRank = 2;

    /// Index type
    using Index = typename Layout::Index;

    /// Long index used for pointer offsets
    using LongIndex = typename Layout::LongIndex;

    /// Coordinate in logical tensor space
    using TensorCoord = typename Layout::TensorCoord;

    /// Stride type
    using Stride = typename Layout::Stride;

    /// TensorRef to matrix object
    using TensorRef = TensorRef<Element, kRank, Layout>;

    /// TensorRef to constant matrix object
    using ConstTensorRef = typename TensorRef::ConstTensorRef;

    /// TensorRef to matrix object
    using TensorView = TensorView<Element, kRank, Layout>;

    /// TensorRef to constant matrix object
    using ConstTensorView = typename TensorView::ConstTensorView;

    /// Diagonal vector
    using Diagonal = Vector<Element, __NV_STD_MIN(kRows, kColumns)>;

private:
public:
    //
    // Methods
    //

    /// Returns the size of the object
    CUTLASS_HOST_DEVICE
    static MatrixCoord extent() { return make_Coord(kRows, kColumns); }

    /// Returns the layout object
    CUTLASS_HOST_DEVICE
    static Layout layout() { return Layout::packed(extent()); }

    /// Ctor
    CUTLASS_HOST_DEVICE
    Matrix() {}

    /// Ctor
    CUTLASS_HOST_DEVICE
    Matrix(Diagonal const& diag) {
        // Todo - construct from diagonal
    }

    /// Returns a TensorRef pointing to the first element of the tensor.
    CUTLASS_HOST_DEVICE
    TensorRef ref() { return TensorRef(this->data(), layout()); }

    /// Returns a TensorRef pointing to the first element of the tensor.
    CUTLASS_HOST_DEVICE
    ConstTensorRef const_ref() const {
        return ConstTensorRef(this->data(), layout());
    }

    /// Returns a TensorRef pointing to the first element of the tensor.
    CUTLASS_HOST_DEVICE
    TensorView view() { return TensorView(ref(), extent()); }

    /// Returns a TensorView to const data
    CUTLASS_HOST_DEVICE
    ConstTensorView const_view() const {
        return ConstTensorView(const_ref(), extent());
    }

    /// Returns a reference to the element at a given Coord
    CUTLASS_HOST_DEVICE
    Reference at(MatrixCoord const& coord) const {
        typename Base::size_type offset_(layout().offset(coord));
        return Base::at(offset_);
    }

    /// Returns the number of scalar elements needed to store tensor.
    CUTLASS_HOST_DEVICE
    LongIndex capacity() const { return LongIndex(Base::size()); }
};

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Column vector defined as a matrix with exactly one column
template <typename Element, int Rows, typename Layout = layout::ColumnMajor>
using ColumnVector = Matrix<Element, Rows, 1, Layout>;

/// Row vector defined as a matrix with exactly one row
template <typename Element, int Columns, typename Layout = layout::RowMajor>
using RowVector = Matrix<Element, 1, Columns, Layout>;

/////////////////////////////////////////////////////////////////////////////////////////////////

}  // namespace thread
}  // namespace cutlass
